The present invention is directed generally toward coal preparation plants and, more particularly, toward an improved screen assembly apparatus for use in coal preparation plants.
Coal preparation plants separate organic and non-organic solid particles by their specific gravities. The coal preparation plant receives a feed of raw mined coal, and separates the raw mined coal into clean coal and refuse. These plants typically utilize two basic processing methods for separating raw coal from rock and varying proportions of striated rock and coal from the higher quality coal. The two processing methods include heavy media and water based separation methods. Heavy media, utilizing a slurry of media, e.g., water and magnetite or ferrosilicon, to separate the coal from the refuse according to their specific gravity of dry solids, is the most common separation process for larger size (Plus 1 mm-0.5 mm) particles. Whereas, water based separation processes are more commonly used for the xe2x80x9ccleaningxe2x80x9d of the finer sized particles, as that term is conventionally understood in the coal processing art. One type of heavy media circuitry used in the coal preparation plants includes a heavy media cyclone.
Coal preparation plants using heavy media cyclones operate with three separate types of screens for coal processing, namely, a deslime screen, a refuse screen and a clean coal screen. A common screening assembly used in many coal preparation plants is today known as a vibratory banana screen. The deslime screen receives the raw coal feed particles and separates them into coarse and fine sized fractions. The coarse or larger sized particles discharged from the screen surface are directed to the heavy media separation section of the coal preparation plant, while the finer sized particles passing through the deslime screen are directed toward the water based separation section of the coal preparation plant.
The separate clean coal and refuse screens receive the clean coal and refuse particles, respectively produced by the heavy media separating section. While on the clean coal and refuse screens, the clean coal and refuse particles are rinsed with water, and the finer particles and water passing through the respective screens are recirculated through the coal preparation plant. Rinsing the clean coal and refuse particles is primarily done to recover the particles of media, such as magnetite, remaining thereon as a result of the coal/refuse separation process, as magnetite can be quite expensive.
Often, the deslime, clean coal and refuse screens are located in different areas of the coal preparation plant and/or on different floors. In addition to being an inefficient use of space and increasing the cost of the coal preparation plant, this situation creates a burden for the plant operator wishing to view the feeds and discharges of raw coal, clean coal and refuse screens.
The present invention is directed toward overcoming one or more of the above-mentioned problems.
In a coal preparation plant which receives a raw coal feed and separates the raw coal feed into clean coal and refuse particles using a media based separation process, an apparatus is provided for use therein. The inventive apparatus simultaneously processes the raw coal feed, clean coal and refuse particles, while occupying minimal floor space within the coal preparation plant. The inventive apparatus includes a unitary vibrating screen assembly having a length and a width, wherein the width of the vibrating screen assembly is partitioned into three screen sections extending the length of the vibrating screen assembly. A deslime screen section receives the raw coal feed particles and separates the raw coal feed particles into coarse and fine sized fractions as the raw coal feed particles move along the length of the deslime screen section. Two separate drain and rinse sections of the screen receive the refuse and clean coal particles, respectively, and remove media remaining on these particles as they move along the length of the respective screen section.
Typically, the various feed particles are moved along the length of the unitary vibrating screen assembly via gravitational and/or vibrating forces. The unitary vibrating screen assembly may be of single or double deck construction, as those terms are conventionally understood in the coal processing art.
In one form, the deslime screen section includes an underpan receiving the fine sized raw coal feed particles passing through the deslime screen section. The fine sized raw coal feed particles received by this underpan are passed to a fine coal, or water based, processing section of the coal preparation plant. The two separate drain and rinse sections each include a separate underpan receiving the media particles which pass through the respective screen section and are recovered from the refuse and clean coal particles. The recovered media particles received by these underpans are recirculated through and/or further processed by the coal preparation plant.
The underpans of the two separate drain and rinse sections may be combined into a single underpan receiving the recovered media particles passing through the screen sections, respectively, for recirculation through and/or further processing by the coal preparation plant.
Sprayers are provided for adding water onto the deslime screen section, and the two separate drain and rinse screen sections to rinse the raw coal feed, refuse and clean coal particles, respectively. Water is used to aid in particle separation in the deslime screen section and also to remove media from the refuse and clean coal particles in the two drain and rinse screen sections, respectively.
In another form, partition members are provided lengthwise along the unitary vibrating screen assembly extending vertically therefrom to partition the unitary vibrating screen assembly into the deslime and the two separate drain and rinse screen sections.
In a preferred form, the inventive unitary vibrating screen assembly includes a multislope xe2x80x9cbananaxe2x80x9d screen of either a single or double deck configuration.
It is an object of the present invention to:
provide an improved screen assembly in a coal preparation plant occupying minimal space; and
to provide an improved screen assembly for simultaneously processing raw coal feed, refuse feed and clean coal feed particles.
Other objects, aspects and advantages of the present invention can be obtained from a study of the specification, the drawings, and the appended claims.